Brent Freidman lays out exactly how to get Time Machine backups to work with any Windows Home Server machine in a point-by-point method that's pretty easy, despite some Terminal tinkering to make it work—follow that here.

If you wanna use just a generic NAS, you can do that too. Personally, I followed this guide by Adam Cohen-Rose—though there are others—to get it going on a 4TB WD ShareSpace several months ago, though WD now has a much cheaper consumer version. It's a hack that also takes a little bit of work, but ditching the USB cable is totally worth it.